PRACTICAL 1: Electrolysis of Copper (II) Sulphate
NAME
: ALIFF HAZIQ BIN JAMARI
MATRIX NO.
: CPM0064_2013B
BATCH
: PRE MED APRIL 2013
GROUP
:C
DATE
:6 SEPTEMBER 2013
th
LECTURER’S NAME : MISS NUR ‘AI N
Objective : To investigate the electrolysis of copper (II) sulphate using copper Electrodes
Introduction :
Electrolysis is the process in which a chemical is broken down into its component chemicals using electricity. It involves submerging two metal electrodes into a liquid or molten substance that contains positive and negative ions. The electrodes connect to a battery. When they are electrically charged, one electrode becomes the negative terminal or cathode, and the other becomes the positive terminal or anode. The positive terminal attracts negatively charged ions and the negative terminal attracts positively charged ions. Electrodes of metal, graphite and semiconductor material are widely used. Choice of suitable electrode depends on chemical reactivity between the electrode and electrolyte and the cost of manufacture.
Apparatus : 1. Batteries (6V) 2. Connecting wires with crocodile clips 3. Ammeter 4. Rheostat 5. Beaker 250ml 6. 1M copper (II) sulphate solution 7. Copper strips 8. Acetone 9. Distilled water 10. Electronic balance 11. Stop watch
Procedure :
1. Two copper strips were cleaned with acetone. Then, they were rinsed with distilled water. Next, the strips were dried completely with filter paper. 2. The strips were weighed and its mass is recorded. 3. The strips are then dipped into 50ml of 1M copper (II) sulphate solution. 4. The electrolytic cell is set up by using batteries, wires, ammeter, rheostat, and two copper strips were dipped in the beaker of copper (II) sulphate solution. 5. The rheostat was adjusted to 1 ampere. The timer was started as soon as the circuit was completed for the reaction. 6. The reaction was leave running for 30 minutes. 7. After that, the copper strips from the solution were removed and were cleaned with acetone. 8. The copper strips were dried completely and it was weighed. The mass was recorded.
Results :
Anode
Cathode
Initial mass of copper strip (g)
0.96
1.75
Final mass of copper strip (g)
0.66
1.94
Mass (g)
0.30
0.19
Discussion : The electrolysis of an aqueous solution of copper sulphate using copper electrodes (i.e. using active electrodes) results in transfer of copper metal from the anode to the cathode during electrolysis. The copper sulphate is ionised in aqueous solution.
2+
CuSO4 ==> Cu + SO4
2-
The positively charged copper ions migrate to the cathode, where e ach gains two electrons to become copper atoms that are deposited on the cathode.
2+
Cu
-
+ 2e ==> Cu
At the anode, each copper atom loses two electrons to become copper ions, which go into solution.
2+
Cu ==> Cu + 2e
-
The sulphate ion does not take part in the reaction and the concentration of the copper sulphate in solution does not change. The reaction is completed when the anode is completely eaten away.
Conclusions : The electrolysis of copper (II) sulphate solution by using copper electrodes produced copper atom that deposited at cathode and caused copper electrode at anode to dissolve i n the solution
Questions :
1. Explain the processes that occurred in the electrolysis of copper (II) sulphate as carried out in the experiment above. Identify the anode and cathode, and write the equations involved. 1.
2. 3. 4.
5.
After the experiment was conducted, it is found that the mass of anode decrease while the mass of cathode increase. This is because when the switch is turned on, copper strip at anode undergoes oxidation and the copper strip at cathode undergoes reduction. The half equation at anode is Cu ==> Cu2+ + 2eThe half equation at cathode is Cu 2+ + 2e- ==> Cu At anode, copper strip is oxidized and dissolved in the copper (II) sulphate solution to form Cu ions. As more copper strip dissolved in the solution to become ions, the mass of the copper strip will decreases. At cathode, copper (II) ions, (Cu ) is reduced to copper metal and deposited on the cathode. The more copper metal deposited on cathode, the more the mass of copper strip increases.
2. Briefly explain 3 uses of electrolysis in industries
The uses of electrolysis are electroplating. Electroplating is used in layering metals to fortify them. Electroplating is used in many industries for functional or decorative purposes, as in vehicle bodies and nickel coins. Next, electrolysis also is important in production of chlorine and sodium hydroxide. Lastly, electrolysis is also used in the cleaning and preservation of old artifacts. Because the process separates the non-metallic particles from the metallic ones, it is very useful for cleaning old coins and even larger objects.
3. State 3 compulsory precautions that should be taken to improve this experiment and the results obtained.
a) Wear gloves when washing the copper strips with the acetone to prevent any impurities stick to the copper strips and dried the copper strips by using filter paper to make sure all the water dry. b) Make sure that all the electrical compartment use is functioning well before the electrolysis process is started. c) Make sure the copper strips at anode and cathode are not overlapping each other when the copper strips are immersed in the beaker containing copper (II) sulphate solution.
References :
1) en.wikipedia.org/wiki/Electrolysis 2) http://curiosity.discovery.com/question/what-is-electrolysis
